Add LookupTimeout configuration to DNS resolver

Gitaly's homegrown DNS resolver triggers DNS queries via UDP. Those
queries run independently in dedicated goroutines. They are controlled
by a timeout context. Recently, the lookup timeout is hard-coded to
15 seconds. This commit adds LookupTimeout configuration to the DNS
   resolver.

Apart from providing a new config to clients, the new config is used to
control and prevent goroutines from being leaked after the test suite is
done. In the grpc-go versions before v1.56, the resolver is closed when
the bound connection is closed. After v1.56, the resolver runs more
independently. The connection doesn't wait for the resolver to finish
anymore. After the test suite finishes, there might be some in-flight
DNS queries are managed by the DNS resolver. When the connection is
closed, those queries don't make sense anymore. They can stay until they
finish. Unfortunately, the goroutine detector in the test suite
complains about leaked goroutines. The resolver of a connection is not
accessible from the outside.

Hence, the test sets a low lookup timeout and sleeps for a while until
the pending DNS queries go away.

1 files changed, 1 insertions, 0 deletions

diff --git a/client/dial.go b/client/dial.go
index 4776109f7..2d7fc18e3 100644
--- a/client/dial.go
+++ b/client/dial.go
@@ -79,6 +79,7 @@ type DNSResolverBuilderConfig dnsresolver.BuilderConfig
 func DefaultDNSResolverBuilderConfig() *DNSResolverBuilderConfig {
 	return &DNSResolverBuilderConfig{
 		RefreshRate:     5 * time.Minute,
+		LookupTimeout:   15 * time.Second,
 		Logger:          logrus.StandardLogger(),
 		Backoff:         backoff.NewDefaultExponential(rand.New(rand.NewSource(time.Now().UnixNano()))),
 		DefaultGrpcPort: "443",